1. Field of the Invention
The present invention relates to a traction control device of a motor vehicle.
2. Description of the Related Art
When the accelerator pedal of a vehicle is abruptly depressed in order to accelerate the engine in a motor vehicle, sometimes slippage occurs at the drive wheels and the tires do not grip the surface of the ground. Thus, slight traction is given to the vehicle. Namely, if slippage occurs at the driven wheels, the drive force for the vehicle body is reduced, and thus a problem occurs in that a correct acceleration of the vehicle cannot be obtained.
To prevent slippage at the driven wheels when the engine is abruptly accelerated, various methods have been proposed, for example, a method in which the output power of the engine is reduced by reducing the amount of fuel fed to the engine cylinders when slippage occurs at the driven wheels. In another method, the output power of the engine is reduced by retarding the ignition timing when slippage occurs at the driven wheels. However, in these methods, the engine operating state is abruptly changed and, as a result, a problem occurs in that engine vibration is generated or the engine is stalled.
A further method of controlling the throttle valve actuated by the accelerator pedal has been considered. In this method, when the throttle valve is fully open to accelerate the engine and slippage occurs at the driven wheels, the throttle valve is compulsorily rotated toward the closed position regardless of the operation of the accelerator pedal and, thereby, the output power of the engine is temporarily reduced. Subsequently, when the slippage of the driven wheels has stopped, the throttle valve is rotated toward the fully open position. However, in this method, the control device for controlling the throttle valve can become inoperative, through damage, etc. and, as a result, the throttle valve may be stuck at the fully open position, and the engine rotates at a full power output. Therefore, a problem occurs in that a safe driving condition is unobtainable. In addition, in the above method, since it is necessary to construct the throttle valve in such a manner that it is actuated by both the accelerator pedal and the control device, the construction of the throttle valve becomes complicated and, therefore, a problem occurs in that it is difficult to obtain a high durability of the throttle valve.